1. Field of the Invention
The invention relates to the hub of a cycle wheel having tension spokes. The invention also relates to a spoked cycle wheel equipped with such a hub.
2. Description of Background and Relevant Information
As is known, a cycle wheel includes an annular rim with a channel for receiving a tire, such as a tubular tire or a more traditional beaded tire, as well as a central hub and spokes for connecting the rim and the hub.
The spokes are tensioned between the hub and the rim, the spoke tension being adjustable, such wheel therefore referred to as a tension spoke wheel.
There are two large families of spokes among the existing types of spokes, viz., straight spokes and bent spokes. The invention relates more particularly to the straight spoke family.
Among the hubs adapted to receive straight spokes are the so-called crenelled hubs. This designation is improper because, rather than crenels, the spokes are retained by radial elements which project with respect to the remainder of the hub body, which form merlons, i.e., a projecting portion between two crenels. The patent documents U.S. Pat. No. 478,394, FR 2 324 471, and FR 2 794 063 disclose such hubs. The merlons make it possible to use straight spokes which, in principle, withstand high tension forces better than bent spokes. They make it possible to orient the spokes tangentially in relation to the hub or along a direction close to tangent. Moreover, the merlon allows off-centering the spoke head with respect to the hub axis, therefore obtaining wider crossing angles and reducing the loading cycles of the spokes during transmission of torque. For the hubs described in the aforementioned documents, two openings extend through the merlons, and the spokes are inserted in a head-to-foot arrangement in each of the openings.
For other hubs with merlons, the merlons are machined with two oriented slots, and the spokes are engaged in the slots so that the heads bear on the ascending front of a merlon. Such a hub is disclosed, for example, in the patent document EP 0 896 886 and family member U.S. Pat. No. 6,189,978.
A hub with slotted merlons of this type enables an easy mounting of the spokes, and therefore facilitates the mounting of the wheel. Indeed, the spokes are not inserted; they are merely engaged.
However, during a ride, one or several spokes sometime lose tension momentarily. This may happen in particular during a frontal, lateral, or a combined impact.
Therefore, it is necessary to provide arrangements that prevent spokes from becoming detached under such a circumstance.
A first arrangement involves providing a small projecting tooth at the top of each of the merlons, which form, with the remainder of each of such merlons, a connection for retaining a spoke head. This mode of construction yields good results but is relatively complex and costly to implement.
Another drawback of the slotted merlon hubs lies in that the head-to-foot arrangement of the spokes causes the spokes to cross one another at a relatively great distance, because the spokes cross one another in the area of the merlons. Therefore, there is a significant unbalance in the tension of the spokes that are connected to the merlons inward of the hub body and those that are connected outward.